The retina serves as an ideal model system for studying neural pattern recognition. It is experimentally accessible, its morphology is well characterized, and in the frog it performs advanced pattern recognition. This research program concerns an analysis of mechanisms for pattern recognition in the frog retina. Intracellular responses to traditional stimuli and to a specially designed random stimulus will be used to infer local circuits within the receptive field of ganglion cells. Light and electron microscopy of cells intracellularly injected with horseradish peroxidase will provide morphological correlation with electrophysiological data. These data will be used to test a local circuit model of nonlinear spatial integration that can account for receptive field trigger features.